On Tue, Nov 24, 2015 at 7:50 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Yeah, but SPF is also used as part of DMARC, which means that merely
> forwarding somebody's email out of our listserv is probably going to look
> like spam, even if we didn't change anything at all about the message
> contents. Also, some sources sign Reply-To: and/or Sender: (Yahoo,
> at least, does the former) which means you can't replace those headers
> either without breaking the DKIM signature. The only fix for that is to
> rewrite From:, and once you do that I don't see a convincing argument why
> you can't also rewrite Subject: and add a footer if you feel like it.
From what I'm reading in DMARC if the DKIM signature is valid then the
email should be accepted regardless of SPF. Many of the sources I'm
reading say that the p=reject Yahoo change only affected lists that
break DKIM signatures. If that's the case then I would say avoiding
breaking DKIM is by far the preferable solution.
Fwiw I think people are by far underestimating the breakage that
rewriting From headers will produce. It breaks assumptions in lots of
places. Just think, you can no longer search for or filter emails from
someone reliably, autoresponders will now respond to the list, if you
Cc the mail then which From header the recipient sees is random, and
so on and so on. I can't imagine the mayhem that cross-posting will
produce. It's just a terrible terrible idea.
--
greg